NR 565 Week 7 And Week 8 Final Exam Study Guide. Antacids: weak bases that react with hydrochloric acid to form salt & water.
o Used in the treatment
... [Show More] of Hyperacidity, GERD, PUD, hyperphosphatemia, and calcium deficiency
o Contain combinations of
metallic cation (aluminum, calcium, magnesium, and sodium)
and basic anion (hydroxide, bicarbonate, carbonate, citrate, and trisilicate)
Pharmacodynamics, Pharmacokinetics, Pharmacotherapeutics
o Neutralize Gastric Acidity (causes ^pH of the stomach and duodenal bulb)
o Inhibit proteolytic activity of pepsin
o Increase lower esophageal sphincter tone
o Acid-neutralizing capacity ANC varies between products expressed in mEqs
o If ingested in a fasting state, antacids reduce acidity for approximately 20 to 40 minutes
o If taken 1 hr after a meal, acidity is reduced for 2 to 3 hrs
o A second dose taken after a meal maintains reduced acidity for more than 4 hrs after the meal
o The action of antacids occurs locally in the GI tract with minimal absorption, minimal metabolism
o ALL antacids are contraindicated in the presence of severe abdominal pain of unknown cause, especially if accompanied by fever
-HIGH SODIUM content: pts w/ HTN, CHF, marked renal failure, or on low-sodium diets need to use low sodium preparation
-Concurrent administration with enteric-coated drugs, destroys the coating= alters absorption, ^ the risk for adverse effects
-Administrations should be separated by at least 2 hours to decrease drug/drug interactions
1. Calcium based antacids: TUMS, Caltrate, Calcarb
• Prescribed to treat calcium deficient states, i.e. chronic renal failure, post-menopause, and osteoporosis
• Used to bind phosphates in CRF
• Require Vitamin D for absorption from the GI tract
• Excreted mainly in feces, 20% in urine
• ADR: Contraindicated in the presence of hypercalcemia and renal calculi
• Can cause constipation- increase bulk, fluids and mobility, stool softener
• Administered 30min- 1hr on empty stomach or 3hr after meals
• Should not be administered with food containing large amounts of oxalic acid (spinach, rhubarb), or phytic acid (bran, cereals), they decrease the absorption of calcium
• Taking w/ foods containing phosphorus (milk, dairy) can lead to milk-alkali syndrome (N/V, confusion, headache).
• Taking with acidic fruit juice improve absorption
2. Aluminum based: AlternaGEL, Amphojel, Mylanta
• Inhibit smooth muscle contraction and slow gastric emptying
• Used to bind phosphates in CRF
• Not absorbable with routine use
• Aluminum concentrated in the CNS
• Bind with phosphate and excreted in feces
• Prolonged use in patients with renal failure may result in dialysis osteomalacia
o Aluminum deposits in bone and osteomalacia occurs
• Elevated aluminum tissue levels contribute to the development of dialysis encephalopathy
• Used to treat hyperphosphatemia in pts w/ renal failure & phosphate renal stone prevention
• Can cause constipation- increase bulk, fluids and mobility, stool softener
3. Magnesium based: Milk of mag, Maalox, Mylanta
• Can be used to treat magnesium deficiencies from malnutrition, alcoholism, or mag-depleting drugs
• Contraindicated in patients with renal failure & used with caution in pts with renal insufficiency
• Not absorbable with routine use
• Excreted in the urine
• Contraindicated in patients with renal failure, use with caution for patients with any degree of renal insufficiency
o Malfunctioning kidney is unable to excrete magnesium and hypermagnesemia may result
• Can cause diarrhea- increase fiber intake (Alkalosis may occur in renal impairment)
Clinical Use and Dosing
Rational drug selection
o ANC, sodium content, and cost
o Combination products with aluminum hydroxide and magnesium hydroxide have the highest ANC (use is moderate to severe disease
Monitoring
o Serum phosphate, potassium, and calcium during chronic use
o These drugs may cause increased serum calcium and decreased serum phosphate
o Chronic magnesium hydroxide use may cause elevated Mg levels in patients with renal failure or the elderly with decreased renal function
Patient education
o Take as prescribed, especially related to mealtimes
o Take 1-3 hrs after meals and at bedtime
o Chewable tablets chew thoroughly and drink half a glass of water
o Shake suspensions before administration
o Many drug interactions, separate doses by 2 hours apart
o Calcium based antacids should not be administer with food containing large amounts of oxalic acid (spinach, rhubarb) or phytic acid (brans, cereals) decrease absorption
o Avoid taking with food containing phosphorus (milk, dairy products) can cause milk-alkali syndrome (NV, confusion, HA)
o Consult provider: before taking antacids for more than 2 weeks if a problem recurs, if relief is not obtained, or if symptoms of GI bleeding (black, tarry stools, coffee ground emesis
o Aluminum and calcium antacids may cause constipation: increase bulk, increase fluid intake, and more mobility, stool softened
o Magnesium antacids may cause diarrhea, increase fiber
o Avoid smoking, avoid flat lying body position while sleeping, foods that irritate the gastric mucosa (spicy foods), or stimulate acid production (alcohol) and foods that decrease lower esophageal sphincter tone (caffeine, chocolate, fatty foods) [Show Less]